1. Technical Field
The present application relates to a technique of speech discrimination ability determination. More specifically, the present application relates to a technique of improving speech-sound discrimination ability and a technique of determining a gain for a hearing aid, for use in hearing aid fitting and the like.
2. Description of the Related Art
Japanese National Phase PCT Laid-Open Publication No. 2008-503261 discloses that a mismatch negativity (MMN) component has come into wide use in developmental studies and sleep studies, as an evoked response testing system for neurological disorders. An “MMN component”, which is a kind of event-related potential contained in an electroencephalogram signal, is a negative potential shift that is mainly induced in 100 ms to 250 ms from the presentation of an auditory stimulation. Since the paradigm for measuring an MMN component does not require the test subject to pay attention to a stimulation, this is suitable for the assessment of an infant or a sleeping user, for whom it is difficult to keep conscious attention.
Japanese Patent No. 4838401 discloses a speech sound intelligibility assessment system. The system described in Japanese Patent No. 4838401 determines the presence or absence of a positive component of event-related potential in a zone from 600 ms to 800 ms since a point in time of presenting a speech sound from an output section, and the presence or absence of a negative component of event-related potential in a zone from 100 ms to 300 ms since a point in time of presenting a speech sound. Based on the result of determining the presence or absence of a positive component and the result of determining the presence or absence of a negative component, an evaluation is made as to whether the user has clearly heard a presented speech sound or not.